None of the 4 Great Chinese Classics are strictly historical fantasy but I think they all have elements of both genres, just in very skewed proportions relative to a historical fantasy written in English.
Now let’s look at each of them in turn. The Journey to the West is a fantasy adventure inspired off the historical event that a monk in the Tang dynasty had travelled to India to bring back Hinduism/Buddhaism texts written in Sanskrit. In fact, I should say that it is a fantasy retelling of this particular historical journey (I’m not sure that the monk had an entourage but I presumed that he did, he was definitely leaning towards being a scholar so he must have needed protection along the way).
The Dream of the Red Chamber is a literary fiction based in an ancient Chinese setting (but not a specific historical period). It details the fall of the aristocratic Jia family and the main plotline revolved around a young male from this family and the tragic fate of the 12 beauties who were related to him. It has got multiple elements: family drama, romance, political intrigue and a touch of the supernatural in that it alludes to the origins of the majority of the main casts being mortal incarnations of immortals.
The Romance of the Three Kingdoms is a historical fiction recounting the main events occurring in the Period of the Three Kingdoms in ancient China which starts from the decline of the Han dynasty. It touches on warfare, personal bravery, loyalty between sworn brothers and romance. Most of the fiction element in this work was in characterisation as opposed to plot. As far as fantasy element goes, there was one major plot point concerning the summoning of an Eastern wind via magic but I always took the interpretation that this person doing the summoning was basically just adept at making weather forecasts.
Water Margins is another historical fiction detailing the rise and fall of a total of 108 outlaws in the Song Dynasty. It is an embellishment of the recorded uprising of about 30 outlaws led by Song Jiang (who appeared in the novel as himself) recorded in real history. Similar to the Romance of the Three Kingdoms, it had little to do with fantasy except for the start which left the hint that the 108 outlaws had some mystical origin as 108 stars of destiny that represented 108 repented demonic lords that were banished by a supreme God in Chinese folk religion and subsequently escaped imprisonment. The theme of immortals escaping to exert major influence in the mortal realms was a somewhat prevalent theme in Chinese folklore and potentially caused by Emperors and Feudal Lords liking to circulate stories of how they are different from birth, hinting that they are chosen by Heaven.
Moonlake's Fiction Space 